resumo
The solid-gas phase photo-catalytic activities of rutile TiO2 and TiOn (1 < n < 2) sub-oxide phases have been evaluated. Varying concentrations of Ti3+ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging from 350 degrees C to 1300 degrees C. The resulting sub-oxides formed were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy and UV-visible diffuse reflectance spectroscopy. The presence of Ti3+ in rutile exposed to high reduction temperatures was confirmed by X-ray diffraction. In addition, a Ti3+-TI4+ system was demonstrated to enhance the photo-catalytic properties of rutile for the degradation of the air pollutants NO2 and CO2 under UV irradiation of wavelengths (A) 376-387 nm and 381-392 nm. The optimum reduction temperature for photo-catalytic activity was within the range 350-400 degrees C and attributed to improved charge-separation. The materials that were subject to carbo-thermal reduction at temperatures of 350 degrees C and 400 degrees C exhibited electrical conductivities over one hundred times higher compared to the non-reduced rutile. The results highlight that sub-oxide phases form an important alternative approach to doping with other elements to improve the photo-catalytic performance of TiO2. Such materials are important for applications such as self-cleaning where particles can be incorporated into surface coatings.
palavras-chave
CARBON-DIOXIDE; TITANIUM-DIOXIDE; PHOTOCATALYTIC REDUCTION; WATER; PERFORMANCE; GEL; CO2; NANOPARTICLES; TI3+; BLUE
categoria
Materials Science
autores
Nuno, M; Adamaki, V; Tobaldi, DM; Gallo, MJH; Otero-Irurueta, G; Bowen, CR; Ball, RJ
nossos autores
David Maria Tobaldi
Investigadoragradecimentos
This research was funded through a University of Bath research studentship. Instrumentation funding was received from the Royal Society, Research grant RG110024. Adamaki and Bowen acknowledge funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement no. 320963 on Novel Energy Materials, Engineering Science and Integrated Systems (NEMESIS). Tobaldi acknowledges the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement.